Method and arrangement for scheduling data packets in a communication network system

ABSTRACT

The present invention relates to a method and an arrangement for scheduling data packets each belonging to a particular traffic class associated with a certain quality of service (QoS) level and transmitted between a first communication network node and a second communication network node. Initially a token rate for assigning tokens to each traffic class is set and an incoming traffic rate of each traffic class is measured by counting a number of incoming data packets during a pre-determined period of time. Then, based on said measured incoming traffic rate said token rate is adjusted in order to obtain a fair scheduling of data packets belonging to different traffic classes.

TECHNICAL FIELD

The present invention relates to a method and an arrangement in acommunication network system and, more particularly, to an arrangementallowing for scheduling data packets as well as a method for suchscheduling.

BACKGROUND

To provide sufficient quality of service (QoS) in an effective, butsimple way is an important issue in the third generation partnershipproject (3GPP) standardization. In Rel 8 of this standard, the QoSconcept is revised and the main difference from the previous concept isthat network initiated QoS profile is introduced and the number ofsignaled parameters over the radio access network (RAN) is significantlyreduced. When a new session is starting then the session initiationprotocol/service discovery protocol (SIP/SDP) is used to signal the QoSneeds to the proxy call session control function (P-CSCF). Then thepolicy and charging rules function (PCRF), using subscription data,formulates the proper QoS profile and forwards it to the relevant nodesin the core network (CN) and RAN.

The QoS profile contains the so-called Label parameter, the AllocationRetention Priority (ARP) parameter, and the uplink-downlink (UL-DL)Maximum and Guaranteed Bit-rate (MBR, GBR). The Label is a simplyinteger (or pointer), which specify a certain QoS class, and it isassociated with a set of QoS parameters in the radio base station (RBS),which are configured by the operator via the operations support system(OSS). Two main types of Labels can be distinguished: GBR Labels, wherethe RAN has to perform admission control; and Non-GBR Label, whichprovides a best-effort type service. The allocation retention priority(ARP) specifies the importance of the bearer setup/modification requestfrom the core network. The MBR specifies the maximum rate that may begiven to this bearer in uplink/downlink respectively. The GBR specifiesthe bit-rate that the RAN should “guarantee” to have available for thisbearer.

Obviously, the basic condition of providing the sufficient QoS is tohandle the RBS resources properly, according to the QoS concept.

FIG. 1 shows how the RBS capacity is divided among the different typesof services. The diagram shows the served traffic, ST, as a function oftime, t. The area of the diagram denoted 10 is the served traffic of GBRbearers, which is the same as the traffic load of the GBR bearers and,the area denoted 12 is the served traffic of the non-GBR bearers, whichis less than or the same as the traffic load of the non-GBR bearers. 18illustrates the aggregated cell capacity as a function of all radioresources and all active users' location. In the following the mainproperties of the RBS capacity management according to the QoS conceptis summarized:

-   -   Basically, the RBS capacity is divided into two main parts,        namely GBR capacity 14, which is fixed and Non-GBR capacity 15        which varies (mapping according to the Label). This division is        allowed by the so-called AAT (Absolute Admission Threshold),        denoted with 16 and which defines a load-level (measured in        kbps) which the aggregate GBR traffic should not exceed during        an average time period;    -   The GBR traffic should be proceed by CAC function using the QoS        descriptor, the current GBR load on the RBS and the AAT value;    -   Both GBR and Non-GBR part of capacity can be divided further        into so-called GBR and Non-GBR partitions;    -   In case of GBR traffic an absolute capacity threshold (like        independent AATs) can be defined for each partition;    -   The non-reserved part of the GBR traffic is distributed among        the Non-GBR partitions. Hence the capacity for Non-GBR traffic        is time varying, so absolute thresholds for the partitions        cannot be defined. Instead the Relative Committed Rate (RCR) is        introduced, which is used to specify the percentage of the total        currently available capacity for each Non-GBR partition;    -   If a non-GBR partition is not fully utilized, then other non-GBR        partitions may share the available resources among them,        according to their RCR value.

The long term evolution (LTE) RAN consists of the following entities: auser equipment (UE), an air interface between the UE and a radio basestation (eNodeB), eNodeB and a RAN transport network with differenttypes of transport equipments between the eNodeB and the CN.

In order to guarantee the sufficient QoS in the LTE RAN adequatescheduling/queuing/resource allocation mechanism and techniques areneeded between the UE and the CN. Basically the UE-CN connection may bedistinguished into two main parts: UE-eNodeB and eNodeB-CN (which hereinis called the LTE RAN transport network) connections.

Between the UE and the eNodeB, the QoS is guaranteed by the UE andeNodeB using proper scheduling mechanisms.

Since the RAN transport network consists of standard (third party)equipments, the QoS may be guaranteed only by using the existing andstandardized functions on a proper way.

FIG. 2 shows a simplified view of the LTE RAN transport network. TheeNodeBs 21 (two are shown in FIG. 2) are communicating with the CN 23via the IP/Ethernet 24 over the S1 interface 25, which is used torealize the transport connections between the eNodeBs 21 and the CN 23.The X2 interface 26 is used to realize the transport connections betweenany two neighbouring eNodeBs 21. Neither the S1 interlace 25 nor the X2interface 26 has flow control. A network management system 28, such asthe OSS-RC, manages the eNodeBs 21 over the Mub interface 29.

The sufficient QoS in the LTE RAN transport network may be provided inthe following ways:

-   -   Simple priority queuing: On IP level the differentiated services        code point (DSCP) field, while on Ethernet level the p-bits may        carry priority information, which is considered in case of        scheduling in the transport nodes. Different types of priority        queuing mechanisms may be used, like strict priority queuing,        weighted fair queuing (WFQ), etc. In WFQ, the resources are        shared between the different queues according to their weight.        The unused resources are divided between the queues which needs        more resources according to their weights.    -   Signalled provisioning: which means that a radio bearer/access        bearer (RB/AB) may only be established when the required        transport capacity is available. The main issues here are the        on-line monitoring of transport resources, informing the radio        level connection admission control (CAC) about the result of        transport level CAC, and reserving the sufficient transport        resources;    -   Bandwidth broker: in this case the CAC decision and network        resource handling is provided by the bandwidth broker, but        obviously it requires an extra equipment in the network;    -   Static provisioning: A simple CAC mechanism is needed into edge        eNodeBs and CNs, but correct operation is guaranteed only by        using proper network dimensioning. This solution—from its static        behaviour—cannot react to the extraordinary situations;    -   Over dimensioning: CAC is not required, however network        utilization is very low, and extraordinary situations cannot be        handled.

The above presented solutions—although those are able to guarantee someQoS level—cannot work together with the LTE QoS concept because of thefollowing reasons:

-   -   Priority queuing provides only simple differentiation but it        does not provide any bandwidth guarantee, which is a basic        requirement for fulfilling the LTE QoS concept;    -   Signalled provisioning, bandwidth broker based solution and        static provisioning is not considered, because it requires extra        interaction between the transport and the LTE devices;    -   Over provisioning is also not sufficient, because it cannot        provide the sufficient QoS level on a cost effective way.

To guarantee proper QoS three main tasks should be solved:

-   -   Correct mapping of radio level QoS information onto transport        level QoS fields (in this case these are DSCP or/and p-bit        field);    -   Proper transport network dimensioning according to the LTE QoS        concept;    -   Proper queuing/scheduling mechanism in the transport nodes for        providing the same traffic classification as in the LTE QoS        concept.

Mapping

If any different GBR or Non-GBR partitions are mapped to the same DSCPor p-bit value then the QoS concept cannot be guaranteed, because incase of packet dropping there is no way to distinguish the trafficpartitions in the transport node, so the individual dropping probabilitycannot be guaranteed any more.

Network Dimensioning

The transport network has been dimensioned such that the GBR traffic maybe handled in any network situation. Since the Non-GBR traffic is abest-effort type of service the non-GBR partitions do not have anyminimum bandwidth requirement in the transport network.

Priority Queuing

The main problems with the priority queuing mechanisms are thefollowing:

-   -   Strict priority queuing is not sufficient, because it does not        make it possible to share the available bandwidth among the        different traffic partitions according to the LTE QoS concept.        The high priority traffic may eat the radio resources.    -   Typically the transport network is not dimensioned for peak cell        rate, because the statistical multiplexing gain is considered.        However, in this case the other queuing mechanisms, like WFQ        cannot guarantee the QoS classification in the transport network        according to the RBS resource distribution.

The critical problem is that the current priority queuing/schedulingmechanisms are not enough to provide the LTE QoS concept. The problemappears if more than one Non-GBR traffic partitions are used and theavailable transport capacity is less than the aggregate traffic of theeNodeBs (the transport is a bottleneck). In this case packet lossoccurs, however the current priority queuing schemes are not able toprovide the same packet loss—in a fair way—for all Non-GBR trafficpartitions, as seen from the following simple example, shown inconjunction with FIG. 3. FIG. 3 shows a first eNodeB 21 a and a secondeNodeB 21 b. Both eNodeBs handles 120 Mbit/s traffic. The first eNodeB21 a is connected to an Ethernet switch 32 in the transport network witha link A having a capacity of 100 Mbps and the second eNodeB 21 b isconnected to the 32 with a link B having a capacity of 100 Mbps. The 32further has a link C connected to an upper level node having a capacityof 180 Mbps. The terms GBR¹, GBR² are the GBR traffic from eNodeB1 andeNodeB2 respectively, NGBR¹ ₁, NGBR² ₁ are the Non-GBR traffic fromeNodeB1 and eNodeB2 respectively for partition 1 and, NGBR¹ ₂ and NGBR²₂ are the Non-GBR traffic from eNodeB1 and eNodeB2 respectively forpartition 1.

Both eNodeBs 21 a, 21 b are able to generate 120 Mbps peak traffic. Thecapacity handling in both eNodeBs is the same:

eNodeB 1 and eNodeB 2 Capacity Capacity for GBR traffic (GBR¹, GBR²) 20Mbit/s Capacity for Non-GBR partition 1 (NGBR¹ ₁, NGBR² ₁) 50 Mbit/sCapacity for Non-GBR partition 2 (NGBR¹ ₂, NGBR² ₂) 50 Mbit/s Totalcapacity 120 Mbit/s 

According to the QoS concept the link capacities will be divided betweenthe different traffic partitions according to the following way:

GBR traffic NGBR partitions Total capacity Link A and B 20 Mbit/s 40Mbit/s for each 100 Mbit/s Link C 40 Mbit/s 70 Mbit/s for each 180Mbit/s

Taking the following traffic situation:

eNodeB 1 GBR¹ NGBR¹ ₁ NGBR¹ ₂ 0 Mbit/s 100 Mbit/s 20 Mbit/s eNodeB 2GBR² NGBR² ₁ NGBR² ₂ 0 Mbit/s  60 Mbit/s 60 Mbit/s

All traffic can be served by the eNodeBs 21 a, 21 b, however thetransport network is a bottleneck. The loss for the NGBR classes is onlink A and B, respectively:

Link A NGBR¹ ₁ NGBR¹ ₂ 20% (100 Mbit/s→ 80 Mbit/s)  0% (20 Mbit/s → 20Mbit/s) Link B NGBR² ₁ NGBR² ₂ 17% (60 Mbit/s → 50 Mbit/s) 17% (60Mbit/s → 50 Mbit/s)

The loss for the aggregated traffic of the NGBR classes on link C,assuming that both eNodeB's traffic receive equal traffic loss. Thereference capacity for the loss value is the original traffic.

Link C NGBR¹ ₁ NGBR¹ ₂ 33.32% (100 Mbit/s → 67.68  0% (20 Mbit/s → 20Mbit/s) Mbit/s) NGBR² ₁ NGBR² ₂ 20% (60 Mbit/s→ 42.32 Mbit/s) 17% (60Mbit/s → 50 Mbit/s)

To see the loss values of the table it is clearly seen that using fixedscheduling weights in the transport network results in a completelyunfair capacity handling, because the different traffic classes receivedifferent loss in the transport. The fair solution would be if alltraffic classes receive the same loss, which in this case is 25% (240Mbits/s→180 Mbit/s).

One main problem is that the eNodeB resources may be allocated to thedifferent Non-GBR classes in a very flexible way, which cannot bereproduced by the standard scheduling mechanisms, like WFQ.

A possible way could be if the WFQ weight system is periodically updatedaccording to the current traffic situation in the eNodeBs. However thissolution has several significant drawbacks:

-   -   All bearer establishment/modification/release require WFQ weight        updates in some transport nodes.    -   The above modification process requires a central entity, which        maintains an actual resource database for the transport network        and it is responsible for process all configuration changes that        are required.    -   Information changing is needed between the eNodeBs (mobile        network) and the transport network (configuration of transport        nodes), which could be problematic if the mobile and transport        networks are in the hand of different operators.

Consequently, a solution is needed, which does not require any on-linecooperation between the base station and transport devices.

SUMMARY

Accordingly, it is an objective with the present invention to provide animproved method of scheduling data packets each belonging to aparticular traffic class associated with a certain quality of service(QoS) level and transmitted between a first communication network nodeand a second communication network node.

According to a first aspect of the present invention this objective isachieved through a method as defined in the characterising portion ofclaim 1, which specifies that the scheduling of data packets is providedby a method in which a token rate for assigning tokens to each trafficclass is initially set, an incoming traffic rate of each traffic classis measured by counting a number of incoming data packets during apre-determined period of time and, said token rate is adjusted based onsaid measured incoming traffic rate, in order to obtain a fairscheduling of data packets belonging to different traffic classes.

Another objective with the present invention is to provide an improvedarrangement for scheduling data packets each belonging to a particulartraffic class associated with a certain quality of service (QoS) leveland transmitted between a first communication network node and a secondcommunication network node.

According to a second aspect of the present invention this otherobjective is achieved through an arrangement according to thecharacterising portion of claim 7, which specifies that scheduling ofdata packets is provided by an arrangement which comprises means formeasuring an incoming traffic rate of each traffic class by counting anumber of incoming data packets during a pre-determined period of timeand means for initially setting a token rate for assigning tokens toeach traffic class and for adjusting said token rate based on saidmeasured incoming traffic rate, in order to obtain a fair scheduling ofdata packets belonging to different traffic classes.

Further embodiments are listed in the dependent claims.

Thanks to the provision of a method and an arrangement, which provide aQoS handling between the user equipment and the access gateways, a fairresource handling among different traffic classes is obtained.

Still other objects and features of the present invention will becomeapparent from the following detailed description considered inconjunction with the accompanying drawings. It is to be understood,however, that the drawings are designed solely for purposes ofillustration and not as a definition of the limits of the invention, forwhich reference should be made to the appended claims. It should befurther understood that the drawings are not necessarily drawn to scaleand that, unless otherwise indicated, they are merely intended toconceptually illustrate the structures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein like reference characters denote similarelements throughout the several views:

FIG. 1 is a diagram of the handling of the aggregate RBS capacity in LTEQoS concept;

FIG. 2 shows a simplified view of the LTE RAN transport system;

FIG. 3 illustrates a simple network topology;

FIG. 4 shows a scheduling architecture according to the presentinvention;

FIG. 5 shows a scheduling mechanism according to the present invention;

FIG. 6 is a flowchart showing the inventive method steps;

DETAILED DESCRIPTION

A communication system, such as a Long Term Evolution (LTE) system shownin FIG. 2, including a Radio Access Network (RAN), comprising at leastone Radio Base Station (RBS) (or eNode B) 21. The RAN is connected overan interface such as the S1-interface 25 to a mobile core 23, which isconnected over the Gi-interface to the external networks such as thePublic Switched Telephone Network (PSTN) or the Integrated ServicesDigital Network (ISDN), and/or a connectionless external network as theInternet.

The RAN and the mobile core provide communication and control for aplurality of user equipments (UE). The UEs each uses downlink (DL)channels and uplink (UL) channels to communicate with at least one RBSover a radio or air interface.

According to a preferred embodiment of the present invention, thecommunication system is herein described as a LTE system. The skilledperson, however, realizes that the inventive method and arrangementworks very well on other communications systems as well and may beapplied in WLAN, Bluetooth, WiMAX etc, The user equipments may be mobilestations such as mobile telephones (“cellular” telephones) and laptopswith mobile termination and thus can be, for example, portable, pocket,hand-held, computer-included or car-mounted mobile devices whichcommunicate voice and/or data with the RAN.

The main goal of the present invention is to provide an architecture andscheduling concept for transport devices (routers, switches) usingpriority queuing, which provides that the RAN transport will be able toguarantee QoS according to the LTE QoS concept.

-   -   The invention also proposes a mapping between packets belonging        to different traffic partitions of eNodeBs and appropriate DSCP        and p-bit values. The basic rule is that all different traffic        partitions need to map different DSCP/p-bit value in order to        provide the differentiation among them in the transport network        devices.    -   A simple transport network dimensioning rule of thumb is also        presented, which is sufficient for realizing the correct LTE QoS        concept by the transport network. The capacity of a current link        is at least the sum of the AAT values of the eNodeBs, which are        served by the current link; this is needed to serve the        guaranteed bit-rate services in any case (failure situations are        not considered). In case of tree topology it is a simple        summarization, however, in case of more generic (e.g.        two-connected network) in the knowledge of the routing strategy        the transport links may also be dimensioned in a simple way.        Obviously, the Non-GBR services should also be considered,        however, in this case statistical multiplexing gain may be        applied.    -   As main part of the invention a scheduling mechanism is        described, which is able to provide fair scheduling between the        packets belonging to different traffic partitions. The essence        of the mechanism is that the resource reservation in the        transport devices is depending on the current incoming        (short-term, second scale) average rate of the different traffic        classes, instead of the pre-defined weights. The scheduling        method is based on the fact that the calls are accepted by the        eNodeB, according to the current offered traffic by the users        and the radio/eNodeB resources and the incoming traffic into the        LTE transport network is already shaped in the eNodeB.        Consequently, the role of the transport network should be a)        forward as much traffic as possible according to the incoming        rate (from the eNodeB) or b) if the transport is a bottleneck        then this resource limitation needs to be handled on a fair way        between the different Non-GBR traffic classes.

The above three issues are able to provide a homogenous QoSclassification between the UE and the CN in case of IP/Ethernettransport network with WFQ priority queuing.

As discussed above, the main problem with the known schedulingmechanisms is that they cannot follow the dynamicity of the resourcehandling according to the evolved QoS concept. Therefore, a proposedscheduling mechanism is presented below and it is assumed thatDSCP/p-bit mapping and network dimensioning is done according to theproposals described above.

The WFQ weight in the transport network nodes may be adjusted in any way(the proposed mechanism is responsible for the correct trafficclassification and scheduling), but the proposed adjustment is accordingto the same (relative) resource distribution which is applied in theeNodeBs.

The rough sketch of the proposed scheduling architecture is seen in FIG.4 for the case of one GBR and three Non-GBR traffic partitions.

The detailed operation of the method is the following:

Incoming packets 40 are distributed from distribution means 41 intodifferent queues 42 a-d on the basis of the p-bit/DSCP fields in theheaders of the packets 40. The queue 42 a contains GBR traffic and theother queues 42 b-d contain non-GBR traffic. The first (left sided onthe figure) scheduling mechanism x provides that the GBR traffic w₁ willget the required resources g and the rest of the resources will bedistributed between the Non-GBR classes w₂₋₄ in such a way that allNon-GBR classes will have the same packet loss.

The packets is only forwarded towards the WFQ scheduling part y if thecurrent queue 42 a-d has got enough token 43, otherwise the incomingpackets are discarded, shown as dropped packets 44. The token generationrate r_(T) is C (equal to the outgoing link rate shown in FIG. 3), whichprovides that the WFQ scheduling mechanism y may serve all packets (noloss) or the WFQ scheduling is not necessary any more, since the tokengeneration rate is equal to the outgoing link capacity. Consequently allserved packets may be forwarded on the outgoing link, the WFQ schedulermay cause re-ordering of packets but no packets will be dropped. Thus,the served packet (with a token) is directly forwarded to the outgoinglink L having a link rate=C, these forwarded packets are denoted 45 inFIG. 4. The token distribution means 46 is arranged to distribute tokens43 to respective queue 42 a-d and the token rate for each traffic classis set individually based on the incoming traffic rate.

The novelty of the scheduling mechanism is the token distributionprocess (shown as 46 in FIG. 4) between the GBR 42 a and Non-GBR 42 b-dqueues, which is seen in FIG. 5.

The token rate r_(T) for the GBR traffic class 51 is guaranteed (thiscomes from the guaranteed bit rate definition), because it is arequirement to provide loss-free transport for the GBR traffic (exceptof the extraordinary situations, like multiple failures, etc). However,if the current GBR rate is less than the AAT rate, r_(A), then theavailable GBR resources (tokens) 43 may be used by the Non-GBR trafficclasses 52. 53 illustrates the GBR burst size and GBR tokens are onlyused when there is GBR data packets in the queue 42 a.

As mentioned, the transport network should carry as much traffic comingfrom the eNodeBs as possible. If the transport is a bottleneck then theavailable resources is divided between the Non-GBR classes according totheir rate r_(N1-N3), which represents the actual resource allocation inthe eNodeB/cell. The transport network follows this resource handling ifthe goal is to provide the QoS/resource allocation between the UE andthe CN according to the evolved QoS concept.

Consequently, the token rates r_(N) for the Non-GBR classes are based ontheir current (second scale average) incoming rate. Furthermore, theavailable GBR tokens, o, are divided among the Non-GBR classes accordingto the incoming rate of the Non-GBR classes. The number of usable tokensby each Non-GBR class needs to be re-calculated in a rate calculationunit 55 from time-to-time to handle the bursty behaviour of the trafficas well as the connection setups and releases. If a packet loss isoccurred in Non-GBR, traffic class, while there was no traffic loss inthe others, then in the next second (period) the token rate for Non-GBR,traffic class will be increased in order to equalize the packet lossamong the Non-GBR traffic classes.

The measurement of the current incoming rate of the Non-GBR classes isthe task of the rate calculation unit 55, which simple counts the numberof incoming packets during a period in each traffic class. Then thisvalue is forwarded to a token classifier 54, which adjusts the currenttoken rate for the Non-GBR classes based on the measured incomingtraffic rate.

The token rate calculation for a Non-GBR class is as follows:

C(N_GBR_token) denotes the default token rate for Non-GBR classes,C(N-GBR_(i)) denotes the current measured incoming rate of N-GBR_(i)class, while TR(N-GBR_(i)) denotes the token rate to be calculated forN-GBR, class, and M is number of different Non-GBR classes.

$\begin{matrix}{{{TR}^{'}\left( {N - {GBR}_{i}} \right)} = {\frac{C\left( {N - {GBR}_{i}} \right)}{\sum\limits_{j \in M}{C\left( {N - {GBR}_{j}} \right)}} \cdot {C\left( {{N\_ GBR}\; {\_ token}} \right)}}} & (1)\end{matrix}$

If one or more Non-GBR class(-es) do not use their all available tokensthen these tokens can be distributed between the N-GBR classes, whichhave unserved packets in their buffer based on their incoming rate. LetP denote the number of those N_GBR classes, which do not used all theirtokens, let Q denote the number of those N_GBR classes, which haveunserved packets in the buffer. (P+Q are not necessarily equal to Mbecause it is possible that N_GBR classes used all tokens and theirbuffer is empty, all packets were served). Then,

$\begin{matrix}{{{{{TR}^{''}\left( {N - {GBR}_{i}} \right)} = {\frac{C\left( {N - {GBR}_{i}} \right)}{\sum\limits_{k \in Q}{C\left( {N - {GBR}_{k}} \right)}} \cdot {C\left( {{{available}\mspace{14mu} N} - {{GBR}\mspace{14mu} {tokens}}} \right)}}},{i \in Q}}\mspace{14mu}} & (2)\end{matrix}$

If the current GBR rate is less than the AAT bit rate then the availabletokens may also be distributed between those Non-GBR classes, which needmore resources in the following way.

$\begin{matrix}{{{{{TR}^{'''}\left( {N - {GBR}_{i}} \right)} = {\frac{C\left( {N - {GBR}_{i}} \right)}{\sum\limits_{i \in Q}{C\left( {N\_ GBR}_{i} \right)}} \cdot {C\left( {{available}\mspace{14mu} {GBR}\mspace{14mu} {tokens}} \right)}}},{i \in Q}}\mspace{14mu}} & (3)\end{matrix}$

Then the token rate for a given Non-GBR class is simple the sum of theabove rates:

TR=TR′+TR″+TR′″  (4)

Obviously, the bursty behaviour of the incoming traffic causes thatperfect token distribution is not possible to adjust, however in longerterm, through several token rate adjustment periods the same averagepacket loss rate same for all Non-GBR traffic classes can be guaranteed.

A procedure of scheduling data packets each belonging to a particulartraffic class associated with a certain quality of service (QoS) leveland transmitted between a first communication network node and a secondcommunication network node, as shown in FIG. 6, is as follows:

-   -   initially setting a token rate for assigning tokens to each        traffic class (step 61);    -   measuring an incoming traffic rate of each traffic class by        counting a number of incoming data packets during a        pre-determined period of time (step 62);    -   adjusting said token rate based on said measured incoming        traffic rate, in order to obtain a fair scheduling of data        packets belonging to different traffic classes (step 63).

The method is applicable in eNodeB, the gateway and the transportdevices, such as routers and switches, between eNodeB and the gateway inthe RAN if the outgoing link capacity of the current device is lowerthan the sum of the incoming link capacities. That is, if all incominglinks are fully loaded then the outgoing link cannot carry the trafficand losses will occur. In order to provide fair packet loss between thedifferent traffic classes the inventive method is used. The inventivemethod may be used in eNodeB when the link, which connects the eNodeB tothe transport network has less capacity than the radio resources handledby eNodeB.

Thus, while there have been shown and described and pointed outfundamental novel features of the invention as applied to a preferredembodiment thereof, it will be understood that various omissions andsubstitutions and changes in the form and details of the devicesillustrated, and in their operation, may be made by those skilled in theart without departing from the spirit of the invention. For example, itis expressly intended that all combinations of those elements and/ormethod steps which perform substantially the same function insubstantially the same way to achieve the same results are within thescope of the invention. Moreover, it should be recognized thatstructures and/or elements and/or method steps shown and/or described inconnection with any disclosed form or embodiment of the invention may beincorporated in any other disclosed or described or suggested form orembodiment as a general matter of design choice. It is the intention,therefore, to be limited only as indicated by the scope of the claimsappended hereto.

Expressions such as “including”, “comprising”, “incorporating”,“consisting of”, “have”, “is” used to describe and claim the presentinvention are intended to be construed in a non-exclusive manner, namelyallowing for items, components or elements not explicitly described alsoto be present. Reference to the singular is also to be construed torelate to the plural and vice versa.

Numerals included within parentheses in the accompanying claims areintended to assist understanding of the claims and should not beconstrued in any way to limit subject matter claimed by these claims.

1.-12. (canceled)
 13. A method in a communication network node ofscheduling data packets each belonging to a particular traffic classassociated with a certain quality of service (QoS) level and transmittedbetween said communication network node and a second communicationnetwork node, comprising the steps of: initially setting a token ratefor assigning tokens to each traffic class; measuring an incomingtraffic rate of each traffic class by counting a number of incoming datapackets during a pre-determined period of time; and adjusting said tokenrate based on said measured incoming traffic rate, in order to obtain afair scheduling of data packets belonging to different traffic classes.14. The method according to claim 13, further comprising the step ofdistributing said data packets into queues of each traffic classaccording to information obtained from a header of each data packet. 15.The method according to claim 13, wherein the traffic classes aredivided into a first traffic class having a high quality of servicelevel and at least one second traffic class having a lower quality ofservice level than said first traffic class.
 16. The method according toclaim 15, wherein the first traffic class is guaranteed a certain tokenrate and is thus assigned a certain amount of tokens.
 17. The methodaccording to claim 16, further comprising the step of using availableunused tokens assigned to said first traffic class in said at least onesecond traffic class, if said token rate of said first traffic class isbelow a pre-determined threshold value.
 18. The method according toclaim 16, wherein when the second traffic class is divided into two ormore traffic classes having different quality of service levels, furthercomprising the step of distributing available unused tokens assigned tosaid first traffic class between said two or more second trafficclasses, if said token rate of said first traffic class is below apre-determined threshold value.
 19. An arrangement in a communicationnetwork node for scheduling data packets each belonging to a particulartraffic class associated with a certain quality of service (QoS) leveland transmitted between said communication network node and a secondcommunication network node, comprising: means for initially setting atoken rate for assigning tokens to each traffic class; means formeasuring an incoming traffic rate of each traffic class by counting anumber of incoming data packets during a pre-determined period of time;and means for adjusting said token rate based on said measured incomingtraffic rate in order to obtain a fair scheduling of data packetsbelonging to different traffic classes.
 20. The arrangement according toclaim 19, further comprising means for distributing said data packetsinto queues of each traffic class according to information obtained froma header of each data packet.
 21. The arrangement according to claim 19,wherein the traffic classes are divided into a first traffic classhaving a high quality of service level and at least one second trafficclass having a lower quality of service level than said first trafficclass
 22. The arrangement according to claim 21, wherein the firsttraffic class is guaranteed a certain token rate and is thus assigned acertain amount of tokens.
 23. The arrangement according to claim 22,further comprising means for using available unused tokens assigned tosaid first traffic class in said at least one second traffic class, ifsaid token rate of said first traffic class is below a pre-determinedthreshold value.
 24. The arrangement according to claim 22, wherein whensaid second traffic class is divided into two or more traffic classeshaving different quality of service levels, the arrangement furthercomprises means for distributing available unused tokens assigned tosaid first traffic class between said two or more second trafficclasses, if said token rate of said first traffic class is below apredetermined threshold value.